206 
We have examined the loss of range of the a particle in 
passing through several other atoms and molecules, and 
found that in all cases the square root law is fulfilled at least 
as accurately as for the atoms and molecules of the original 
list. The new substances are : — Lead, iron, nickel, oxygen, 
carbon dioxide, carbon bisulphide, ethyl iodide, chloroform, 
pentane, and benzene. 
During the progress of this work, one of us (R. D. Klee- 
man) left Australia for England. We wish to acknowledge 
with gratitude the assistance of Mr. H. J. Prest, B.Sc, in 
completing the observations. 
